Used Strut braces on my 155's and decided not to go for one on the 156. Reason ???..In the wet, the car understeers so much easier with a strut brace fitted.
I also track day my cars and the 156 did great round Knockhill recently without a strut brace....being Knockhill...it was of course wet
The induction kit, zorst thing is talked about a lot on here and other forums as there are a lot of opinions that all seem to make sense, even though they contradict each other.
So here's my opinion/experience of using kits etc. (being my opinion it'll obviously be correct
The only kit I have used that does feel as though it's making a proper difference through the rev range is the BMC CDA. These cost about £150.
Used K&N 57i kits, panel filters, you name it. Haven't really found a benefit from them except noise, especially the 57i. Induction kits tend to draw in hot air from the engine bay so reduce performance if anything. Remember when these are tested on a dyno, the bonnet is up and they use huge fans to blow cold air, so not like driving on the road.
Modifying induction kits.....I wouldn't do this either unless you know exactly what length induction you want. Lengthening the intake length is supposed to give slightly better low down torque but at the expense of being able to rev it up to the redline. Making it shorter apparently does the opposite. It's also not quite as simple as that due to "pulse tuning". Get it wrong and the air pulses go all to pot and actually hinder air intake. You can "google" this on the net.
Exhausts...........use one that is made specifically for the car and not made to fit the car in a workshop. I've used Powerflow before and wouldn't again. Also use a bore that is the same as the OE pipe.
Bigger bore is NOT always better, again due to pulse tuning. Wider bore allows the escaping gas to cool down more, the cooler the air, the slower it moves. It's this air movement that creates a vacuum behind each pulse and therefore drags the next pulse along with it. So slower air movement, less vacuum, gas escapes slower.
Putting on kits and zorsts won't really do anything great for performance overall. To get the best out of whatever you buy, the engine would need a "real time" remap to tune it perfectly to your mods.
OK I'm getting sore fingers now.........